Detect availability of intrinsics on intel macs just in case

kitty/simd-string.c

@@ -243,8 +243,12 @@ init_simd(void *x) {
     PyObject *module = (PyObject*)x;
 #define A(x, val) { Py_INCREF(Py_##val); if (0 != PyModule_AddObject(module, #x, Py_##val)) return false; }
 #ifdef __APPLE__
-    // Modern Apple Intel processors should all support AVX2. And simde takes care of NEON on Apple Silicon
+#ifdef __arm64__
+    // simde takes care of NEON on Apple Silicon
     has_sse4_2 = true; has_avx2 = true;
+#else
+    has_sse4_2 = __builtin_cpu_supports("sse4.2") != 0; has_avx2 = __builtin_cpu_supports("avx2");
+#endif
 #else
 #ifdef __aarch64__
     // no idea how to probe ARM cpu for NEON support. This file uses pretty

kitty_tests/main.py

@@ -298,6 +298,8 @@ def env_for_python_tests(report_env: bool = False) -> Iterator[None]:
     if os.environ.get('CI') == 'true' or report_env:
         print('Using PATH in test environment:', path)
         print('Python:', python_for_type_check())
+        from kitty.fast_data_types import has_avx2, has_sse4_2
+        print(f'Intrinsics: {has_avx2=} {has_sse4_2=}')
 
     with TemporaryDirectory() as tdir, env_vars(
         HOME=tdir,